1. Technical Field
The present invention relates to a method of evaluating a film, and more particularly to a method of evaluating diffusion behavior of hydrogen in the film.
2. Related Art
For a thin film, permeability with respect to hydrogen-related species (H, H2, OH, H2O) is a critical property. In this relation, differential-pressure gas chromatography may be employed to measure the permeability of hydrogen gas or vapor. However, no method has so far been developed for measuring a hydrogen diffusion cross section of an ultra-thin film of a nanometer order such as those in an LSI, especially under a state where the specimen is stacked on a substrate. Based on Resonant nuclear reaction analysis (hereinafter, NRA), which is a process of resolving the depth of the specimen to thereby measure the quantity of hydrogen, for example the non-patented document 1 reports a phenomenon that an NRA signal in a SiO2/Si interface changes depending on primary ion dose.    [Non-patented document 1] Michael A. Briere et al., “A QUANTITATIVE INVESTIGATION OF HYDROGEN IN THE METAL-OXIDE-SILICON SYSTEM USING NRA”, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 37, NO. 6, DECEMBER 1990, pp. 1658-1669    [Non-patented document 2] Susumu Shuto et al., “Impact of passivation film deposition and post-annealing on the reliability of flash memories”, IEEE Proceeding of IRPS 1997, pp. 17-24
The present inventors have recognized as follows. It is known in the semiconductor field that hydrogen imposes a great impact on the reliability of a MOS transistor or the like, and hence a method that provides the hydrogen permeability of the thin film, including an interlayer dielectric film, has been eagerly sought for. Methods of measuring the quantity of hydrogen, however, are limited and practically effective measuring methods have barely been developed. Accordingly, theoretical calculation has usually been the only recourse in estimating the quantity of hydrogen. In this respect, correlation between the refractive index of the film and the hydrogen permeability has recently been focused on, however a theoretically corroborated correlation has not yet been established. Therefore, it is of primary importance to establish a method of directly measuring the hydrogen permeability and other associated properties of the film (for example, refer to the non-patented document 2).